Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
3/19/2013
1
Gavi Night Frog- 1 of 12 newly discovered frogs in India (Nyctibatrachidae)
Julia E. EarlNIMBioS, University of Tennessee
questions: [email protected]
I. Why does it matter?
II. Amphibian Declines: History and Current State
III. Why Amphibians?
IV. Hypotheses for Declines
Required Readings:
Supplemental Readings:
Wells (2007): pp. 787-795, 800-803, 850-853
Wells (2007): pp. 816-853
Important part of the ecosystem◦ Huge amount of biomass Why?◦ Move nutrients between
ecosystems Redback Salamander
Small Mammal Community
Birds at Peak Breeding
0 1 2
Redback …
Small …
Birds at Peak …
◦ Prey◦ Predators Can alter pest populations Change decomposition
rates and thus nutrientcycling
0 50 100 150 200
Pond Amphibian Metamorphs
Black bellied Salamander
Biomass (kg/ha)
0 1 2
References: Peterman et al. 2008; Gibbons et al. 2006; Burton and Likens 1975; Seale 1980; Beard et al. 2002, 2003; Sin et al. 2008; Whiles et al. 2006
3/19/2013
2
Medicine◦ Skin secretions and toxins- major potential for the
development of pharmaceuticals◦ Trials in rats show some of them have applicationsTrials in rats show some of them have applications
for weight loss, blood pressure regulation, cancer fighting, anti-microbial, anti-fungal, congestive heart failure, drug addiction, pain
Touted as ecological indicators◦ May help assess environmental quality◦ Presence of contaminants
History of Amphibian Declines
Prior 1970s:
1970-mid-1980s:
•Few extinctions; some localized die-offs
•Few extinctions
•Localized die-offs in temperate areas associated with habitat destruction
Ohio Journal of Science 49:70-71
Late 80s-Now: •Increase in extinctions
•Localized & regional die-offs in temperate and tropical areas; some in “pristine” areas
Alberta Naturalist 11:1-4
Conservation Biology 7:355-362, 8:72-85, 10:406-413, 10:414-425, 12:106-117, 13:117-125; Biotropica 20:230-235; Nature 404:752-755
1989 First Meeting of the World Congress of Herpetology
Global Amphibian DeclinesHoulahan et al. 2000, Nature 404:752–755
100
150
200
250
r o
f P
op
ula
tio
ns
150
200
250
300
of
Po
pu
lati
on
s
North America Western Europe
0
50
100
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
Nu
mb
er
0
50
100
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
Nu
mb
er
3/19/2013
3
Bufo periglenes Discovered in 1966 in Costa
Rica in the cloud forests ~15,000 were seen for the
next 17 yearsnext 17 years 1988: 10 individuals 1989: 1 individual None seen since Monteverde Cloud Forest
Preserve- very well protected
30% of amphibian species
13% = birds, 21% = mammals
21% = reptiles, 20% bony fish
In Threat of Extinction (2012 data):
From the Global Amphibian Assessment, 2004
3/19/2013
4
3/19/2013
5
Order Total EX EW CR EN VU NT LC DD
% Threaten
ed or Extinct
Anura Frogs & Toads
5,640 32 2 429 665 561 327 2,178 1,446 29.3
Caudata 557 2 0 79 101 92 62 161 60 48 8 Caudata Salamanders & Newts
557 2 0 79 101 92 62 161 60 48.8
GymnophionaCaecilians
177 0 0 1 1 4 0 53 118 3.4
Total 6,374 34 2 509 767 657 389 2,392 1,624 30.3
25%Anura = 1,655 sppCR, EN, or VU:
Caudata = 272 spp
Gymnophiona = 6 spp
2 Salamanders◦ Plethodon ainsworthi- South central Mississippi◦ Cynops wolterstorffi- (Newt) Yunnan, China
34 Anurans ◦ 2 Extinct in the wild- Wyoming toad [7 zoos around
the USA] Kinhasi spray toad (Tanzania) [Toledo Zoo]the USA], Kinhasi spray toad (Tanzania) [Toledo Zoo]◦ 20 spp. of Rhacophorids- 1 just rediscovered in Sri
Lanka after 160 years of no detection (March 5, 2013)◦ 4 spp. Bufonids, 3 Myobatrachids, 2 Craugastorids,
and 1 Hylid, Ranid, and Dicroglossid Plus 54 species that haven’t been seen in 5-40yrs,
mostly in Latin America: see the MIA section http://amphibiaweb.org//declines/extinct.html
Status of U.S. Amphibians
•2 Species Extinct (R. fisheri; P. ainsworthi)
•10 Endangered (+3 subspp, 3 pop.); 9 Threatened (+1 pop.); 5spp and 2 pop. Awaiting
•Of the E,T: 4 in Puerto Rico, 8 in CA, 6 in SW, 6 in SE, 1 in MO and 1 in WY
Western U.S.
•TN: 1 state-listed out of 26 spp (30%)
3/19/2013
6
Why are Amphibians so Susceptible?
Exothermic vertebrates with a biphasic (in part) life cycle
•Thin, Permeable Skin that must remain Moist
•Low Vagility (<1 km)
1) Respiration
2) Osmoregulation
•Long-lived (ca. 10 yr)
Desiccation is a Lifelong
Struggle
Absorb Compounds
Readily
Hypotheses Related to DIRECT Anthropogenic
Effects
Habitat Destruction/Degradation Hypothesis
Obvious: •Agricultural Practices
•Urban Development
54% Wetlands
Loss
•Draining, Filling, Altering Wetlands
•Barriers between aquatic and
•Deforestation (R. Semlitsch, LEAP)
aquatic and terrestrial habitat•Fragmentation
Destroying Terrestrial Habitat (30 yrs)
-Plethodontids especially vulnerable
- Some debate about how much direct mortality, evacuation, underground (Petranka)
3/19/2013
7
Not so Obvious:
•Sedimentation (deforestation, urban development, agriculture, roads)
-Fill in interstitial spaces, inhibit O2 uptake
•Altered Hydroperiods
Can occur from changes in vegetation nearby or-Can occur from changes in vegetation nearby, or
changes in groundwater
•Wildlife Management
•Burning- Still not much known about controlled burns- direct mortality, reduced leaf litter, microclimate
•Mowing
•Soil Compaction –burrow useJWM
64:615-631
Chemical Pollution HypothesisPoint Source:
Non-point Source:
Pollution originating from 1 point.
•Effluent: organic or industrial waste
•Thermal: electric plants
Pollution originating from multiple points (e.g., field, parking lot).
Chemicals & Effects:
Sublethal
•Nitrates & Ammonia: Direct mortality; Reduce growth
•Organophosphate Insecticides: Above plus malformations and altered behavior
•Atrazine: Most widely used herbicide in the world. Endocrine disruption, eggs in testes, at very low doses (Tyrone Hayes)
•Various Oils & Compounds: Affect respiration
Chemicals & Effects: Relyea (2003, 2004, 2005, 2009), Boone, Rohr
Interactive effects with
Natural Stressors
Introduced Predators & CompetitorsHypothesis
Predators:•Fish (eat everything)
• Intentionally stocked all over the world. In montane regions, often by airplane. In western USA- 60% of montane and 90% of large lakes.
•Bullfrogs (eat everything but adults) – Introduced S. America,
Sport Fish (e.g. trout, bass)
( y g )Europe, and Asia. Also, concern that they spread disease.
•Fire Ants (eat metamorphs)
Copeia 1999:22-23
Copeia 1991:1-8
SARI Spec. Pub. 1
3/19/2013
8
American Bullfrog Distribution
•Frogs – competitors in the aquatic stage. B. marinus also is toxic in all stages-not very good prey…
•Bait & Mosquito Fish – New research show they can attack ranids, causing prolific injuries
•Crawfish (Predator of eggs also) - Also alter habitat quality by shredding aquatic vegetation.
Bufo marinus, L. catesbeianus
Other Invaders: -Primarily plants. Can contain toxic compounds that leach into ponds. Alter terrestrial habitat structure
-Earthworms (NE USA): accelerate leaf decomposition,
depriving salamanders of moisture and cover
Conservation Biology 13:613-
622 FROGLOG
15 & 17
Food –Mainly for frog legs, but also Andrias◦ Domestic Consumption: SE Asia, Latin
America◦ Major importers: EU (Belgium, France) 4.6
thousand tons/yr (about 10-100millions frogs/yr), USA 4.3 thousand tons/yr, Japan
◦ Major exporter: Indonesia (84% of EU’s consumption), China/Taiwan (81% of USA’s bullfrog imports), Mexico (43% of USA’s other frog imports, mostly wild caught)
◦ These data are up to date. Historically, most amphibian imports came from India and Bangladesh, but a ban went into effect in 1987 and 1989.
Resource: “Canape’s to Extinction: The International Trade in Frog’s Legs and its Ecological Impact” 2011, report by the Defender’s of Wildlife
3/19/2013
9
Pets: Wild caught primarily consist of W. Dwarf African clawed frogs (2.4 million), Chinese Fire Belly Newt (1.6 mil), Oriental Fire Belly Toad (1mil), stats are imported to USA from 1998-2002 [Bioscience 55(3): 256-264, 2005]
Bait: ex. tiger salamanders and Desmognathus in the USA◦ Used by up to 73% of anglers in the SW◦ Spread Chytridiomycosis [Cons. Bio. 22(6): 1582-9]
Research/Teaching- biological supply companies◦ Primarily bullfrogs, n. leopard frogs, and mudpuppies◦ As of 2003, only 1 of 14 companies sold only farm-raised
Lots of data challenges, also indirect effects- release, disease spread
Hypotheses Related to INDIRECT Anthropogenic
EffectsEffects
Global Warming Hypothesis• The anthropogenic increase of ambient temperatures via the accumulation of “greenhouse” gases.
• Expected to increase temperatures (1.5-5.8°C) by 2100, increase weather severity, generally change weather patterns.
CO2, N2O, CH4
Consequences of Greenhouse Effect
•Decreased/altered hydroperiods
•Some amphibians may have a lower ability to shift their ranges with the climate due to
low dispersal ability
•High altitude/lattitude
•Ectotherms
•A LOT OF UNCERTAINTY
Catastrophic Events
Climate Change 39:541-561
3/19/2013
10
UV-B Radiation Hypothesis• Ozone depletion has resulted in increased incidence of UV-B radiation with the surface of Earth.
• Damages DNA and other cellular processes
• Higher amounts of melanin (dark pigment) is protective.
Effects on AmphibiansBlaustein
Effects on Amphibians
•Direct Mortality
•Decrease Hatching Success***
•Malformations
Most Susceptible Amphibians:
•Low Photolyase in Eggs (DNA repair)
•Eggs Near Surface
•Higher Elevation
Photochemistry & Photobiology 64:449-456
Conservation Biology 10:1398-1402Vegetation
Acid Precipitation Hypothesis• The anthropogenic decrease in pH of precipitation via emissions of nitrogen oxides and sulfur dioxide and their oxidation and dissolution to acids.• Disrupts ion balance, also associated with high concentrations of dissolved heavy metals, e.g. Al
Effects on Amphibians pH < 4
•Direct mortality
•Delayed hatching
•Reduced mobility
•Reduced larval growth rate & size
Food WebCopeia 1986:454-466
Chytrid (KI-trid) FungusPathogenic Hypothesis: Fungi
Non-hyphal, Parasitic Fungus
Phylum: Chytridiomycota
Class: Chytridiomycetes
Order: Chytridiales
Unicellular
Most Haploid: Zoospores
Batrachochytrium dendrobatidis
Proc. Natl. Acad. Sci. 95:9031-9036
Colonize Keratinized Epidermal Cells (Mouth & Pelvic Patch)
Effects on Amphibians
•50-100% Direct Mortality
•Biggest problem in Central America, Australia
Epidermal Hyperplasia Sloughing
Interference w/ CutaneousRespiration & Osmoregulation
3/19/2013
11
•dsDNA, 150-280K bp
•120-300 nm in diameter (3x smaller than bacteria)
•Icosahedral Shape (20)
Family: Iridoviridae Chinchar et al. (2006)
Granoff et al. (1965); Rafferty (1965) Jancovich et al. (1997)Docherty et al. (2003)
Pathogenic Hypothesis: Iridovirus
Family: Iridoviridae
Species (6)
Ambystoma tigrinum virus (ATV)Bohle iridovirus (BIV)
Frog virus 3 (FV3)
Virion
Iridovirus, Chloriridovirus, Ranavirus, Megalocytivirus, and LymphocystivirusGenera: Invertebrates Ectothermic Vertebrates
Paracrystalline Array
Amphibian Declines
Signs:1) Dermal ulcerations and edema 2) Systemic hemorrhages
Pathogenic Hypothesis: BacteriaThought to be Secondary to Viral and Fungal
Infections Aeromonas hydrophila
•Ubiquitous
•Facultatively Anaerobic
•Oxidase-positive
•Gram-negative
“Red-Leg”
Enters host via Ingestion
Effects on Humans: gastroenteritis & septicemia
Effects on Amphibians:
1) Stop Eating
2) Septicemia
3) Capillary Dilation
4) PetechialHemorraging
Associated w/ “Stress”
3/19/2013
12
TrematodesPathogenic Hypothesis: Parasites
(Ribeiroia ondatrae)
Effects on Amphibians41 spp.
1) Cysts form in and around “limb-buds”
2) Limb Development
Science 284:802-804
2) Limb Development
3) Malformations
- Can cause localized problems
Survival/Reproduction
P. Johnson
Many of these go together For example-◦ Deforestation can lead to stream sedimentation, increased
UV light getting through, changes in hydroperiod, encroachment by invasive species
◦ Agriculture can increase chemical loads, sedimentation, parasite loads invasive speciesparasite loads, invasive species
◦ All of which can be further complicated by disease, acid rain and global warming
These effects can be additive (can predict) or interactive (much harder to predict)
The Synergistic Hypothesis
Habitat
InvasiveSpeciesPathogen
Likely a Synergy of
Anthropogenic Effects
Some Factors may Suppress
Immune System via
“Stress”
Pollution
GlobalWarming
UVB
ExploitAcidRain
Some Factors may increase
Toxicity/Virulenceof other Factors
Local Population Loss increases Probability of
MetapopulationExtinction Annu. Rev. Ecol. Syst.
30:133-165
3/19/2013
13
What can you do?Amphibian Population Declines
Participate in Surveys
Bob English; 615-395-4166Tennessee:GC20 @ [email protected]
Other Activities-Use good practices around your home and encourage others as well http://www.fws.gov/contaminants/Documents/Homeowners_Guide_Frogs.pdf-Don’t release pets or bait into the wild-Lots of other ideas:
In Conclusion